This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The role of SIV-specific cellular immune responses in maintaining nonpathogenic SIV infection in sooty mangabeys is being investigated in naturally SIV-infected sooty mangabeys and experimentally SIV-infected rhesus macaques using Elispot and intracellular cytokine staining assays as well as by in vivo CD8-positive T lymphocyte depletion studies.